A transparent conductive film in which a transparent and conductive thin film is laminated on a base formed of a transparent plastic film has been widely used in an application utilizing conductivity thereof, for example, a flat panel such as a liquid crystal display, or a touch panel to be mounted on a smart phone, a car navigation system and a digital camera.
The touch panel includes an optical type, an ultrasonic type, an electromagnetic induction type, a capacitive type and a resistive type according to a position detection system. A resistive touch panel has a structure in which the transparent conductive film and a glass substrate on which a transparent conductive layer (indium tin oxide (hereinafter, abbreviated as “ITO”)) is laminated are opposed through a dot spacer. When the transparent conductive film is pressed, the transparent conductive layer (ITO) on one of opposed glass substrates and the transparent conductive layer (ITO) of the transparent conductive film on the other of opposed glass substrates are electrically connected on a point where the dot spacer is absent, and thus a position is determined. Therefore, a service life due to a decrease in strength of the dot spacer or ITO becomes problematic. On the other hand, a capacitive touch panel has on a base a transparent conductive layer subjected to patterning. When the panel is touched with a finger or the like, a capacitance of the finger is detected to cause a change of a resistance value between a touched point and the transparent conductive layer subjected to patterning, and thus two-dimensional position information is accurately detected. Owing to the structure, the panel has features of having no movable part, and has a high reliability, a long service life, and excellent optical features such as transparency.
As described above, for the touch panel, predetermined patterning is applied to the transparent conductive layer or the like of the transparent conductive film in some cases in order to detect an input position. However, patterning clearly defines optical characteristics between a patterned part (part in which the transparent conductive layer or the like exists) and a non-patterned part (pattern opening part in which the transparent conductive layer or the like is removed), and appearance as a display device is potentially deteriorated. In particular, according to the capacitive touch panel, the transparent conductive layer is formed on a front face of a display part. Therefore, a panel having a good appearance even when the transparent conductive layer is subjected to patterning is required therefore.
The transparent conductive film that has so far been applied includes a transparent conductive film having a film on which a conductive layer is formed, a conductive layer, an undercoat layer (except for a layer having conductivity) composed of a metal oxide as formed between the film on which the conductive layer is formed, and the conductive layer, and a metal layer composed of a single metal element or an alloy containing two or more kinds of metal elements including at least one kind contained in the metal oxide as formed between the undercoat layer and the film on which the conductive layer is formed (Patent literature No. 1, paragraph 0007). As a specific example, a constitution is disclosed in which a 1 nm-thick silicon layer, a 60 nm-thick zinc oxide-tin oxide layer, a 45 nm-thick silicon oxide layer, and a 30 nm-thick ITO layer are sequentially laminated on a face on one side of a PET film (see Patent literature No. 1, for example).
As one of other transparent conductive films, a transparent conductive film is also disclosed in which at least a high refractive index layer, a low refractive index layer and a transparent conductive layer are arranged on one face of a transparent plastic film, and a hard coat layer is arranged on the other one face of the transparent plastic film, and a hard coat layer is arranged between the transparent plastic film and the high refractive index layer (see Patent literature No. 2, for example).